[PATCH bpf-next v5 1/2] bpf: refactor max_depth computation in bpf_get_stack()

[PATCH bpf-next v5 1/2] bpf: refactor max_depth computation in bpf_get_stack()

[Arnaud Lecomte]

A new helper function stack_map_calculate_max_depth() that
computes the max depth for a stackmap.

Changes in v2:
 - Removed the checking 'map_size % map_elem_size' from
   stack_map_calculate_max_depth
 - Changed stack_map_calculate_max_depth params name to be more generic

Changes in v3:
 - Changed map size param to size in max depth helper

Changes in v4:
 - Fixed indentation in max depth helper for args

Changes in v5:
 - Bound back trace_nr to num_elem in __bpf_get_stack
 - Make a copy of sysctl_perf_event_max_stack
   in stack_map_calculate_max_depth

Link to v4: https://lore.kernel.org/all/20250819162652.8776-1-contact@arnaud-lcm.com/

Signed-off-by: Arnaud Lecomte <contact@arnaud-lcm.com>
Acked-by: Yonghong Song <yonghong.song@linux.dev>
---
 kernel/bpf/stackmap.c | 28 ++++++++++++++++++++++++----
 1 file changed, 24 insertions(+), 4 deletions(-)

diff --git a/kernel/bpf/stackmap.c b/kernel/bpf/stackmap.c
index 3615c06b7dfa..796cc105eacb 100644
--- a/kernel/bpf/stackmap.c
+++ b/kernel/bpf/stackmap.c
@@ -42,6 +42,28 @@ static inline int stack_map_data_size(struct bpf_map *map)
 		sizeof(struct bpf_stack_build_id) : sizeof(u64);
 }
 
+/**
+ * stack_map_calculate_max_depth - Calculate maximum allowed stack trace depth
+ * @size:  Size of the buffer/map value in bytes
+ * @elem_size:  Size of each stack trace element
+ * @flags:  BPF stack trace flags (BPF_F_USER_STACK, BPF_F_USER_BUILD_ID, ...)
+ *
+ * Return: Maximum number of stack trace entries that can be safely stored
+ */
+static u32 stack_map_calculate_max_depth(u32 size, u32 elem_size, u64 flags)
+{
+	u32 skip = flags & BPF_F_SKIP_FIELD_MASK;
+	u32 max_depth;
+	u32 curr_sysctl_max_stack = READ_ONCE(sysctl_perf_event_max_stack);
+
+	max_depth = size / elem_size;
+	max_depth += skip;
+	if (max_depth > curr_sysctl_max_stack)
+		return curr_sysctl_max_stack;
+
+	return max_depth;
+}
+
 static int prealloc_elems_and_freelist(struct bpf_stack_map *smap)
 {
 	u64 elem_size = sizeof(struct stack_map_bucket) +
@@ -438,10 +460,7 @@ static long __bpf_get_stack(struct pt_regs *regs, struct task_struct *task,
 		goto clear;
 	}
 
-	num_elem = size / elem_size;
-	max_depth = num_elem + skip;
-	if (sysctl_perf_event_max_stack < max_depth)
-		max_depth = sysctl_perf_event_max_stack;
+	max_depth = stack_map_calculate_max_depth(size, elem_size, flags);
 
 	if (may_fault)
 		rcu_read_lock(); /* need RCU for perf's callchain below */
@@ -460,6 +479,7 @@ static long __bpf_get_stack(struct pt_regs *regs, struct task_struct *task,
 		goto err_fault;
 	}
 
+	num_elem = size / elem_size;
 	trace_nr = trace->nr - skip;
 	trace_nr = (trace_nr <= num_elem) ? trace_nr : num_elem;
 	copy_len = trace_nr * elem_size;
-- 
2.43.0

[PATCH bpf-next v5 2/2] bpf: fix stackmap overflow check in __bpf_get_stackid()

[Arnaud Lecomte]

Syzkaller reported a KASAN slab-out-of-bounds write in __bpf_get_stackid()
when copying stack trace data. The issue occurs when the perf trace
 contains more stack entries than the stack map bucket can hold,
 leading to an out-of-bounds write in the bucket's data array.

Changes in v2:
 - Fixed max_depth names across get stack id

Changes in v4:
 - Removed unnecessary empty line in __bpf_get_stackid

Link to v4: https://lore.kernel.org/all/20250813205506.168069-1-contact@arnaud-lcm.com/

Reported-by: syzbot+c9b724fbb41cf2538b7b@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=c9b724fbb41cf2538b7b
Signed-off-by: Arnaud Lecomte <contact@arnaud-lcm.com>
Acked-by: Yonghong Song <yonghong.song@linux.dev>
---
 kernel/bpf/stackmap.c | 23 +++++++++++++----------
 1 file changed, 13 insertions(+), 10 deletions(-)

diff --git a/kernel/bpf/stackmap.c b/kernel/bpf/stackmap.c
index 796cc105eacb..ef8269ab8d6f 100644
--- a/kernel/bpf/stackmap.c
+++ b/kernel/bpf/stackmap.c
@@ -247,7 +247,7 @@ get_callchain_entry_for_task(struct task_struct *task, u32 max_depth)
 }
 
 static long __bpf_get_stackid(struct bpf_map *map,
-			      struct perf_callchain_entry *trace, u64 flags)
+			      struct perf_callchain_entry *trace, u64 flags, u32 max_depth)
 {
 	struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map);
 	struct stack_map_bucket *bucket, *new_bucket, *old_bucket;
@@ -263,6 +263,8 @@ static long __bpf_get_stackid(struct bpf_map *map,
 
 	trace_nr = trace->nr - skip;
 	trace_len = trace_nr * sizeof(u64);
+	trace_nr = min(trace_nr, max_depth - skip);
+
 	ips = trace->ip + skip;
 	hash = jhash2((u32 *)ips, trace_len / sizeof(u32), 0);
 	id = hash & (smap->n_buckets - 1);
@@ -322,19 +324,17 @@ static long __bpf_get_stackid(struct bpf_map *map,
 BPF_CALL_3(bpf_get_stackid, struct pt_regs *, regs, struct bpf_map *, map,
 	   u64, flags)
 {
-	u32 max_depth = map->value_size / stack_map_data_size(map);
-	u32 skip = flags & BPF_F_SKIP_FIELD_MASK;
+	u32 elem_size = stack_map_data_size(map);
 	bool user = flags & BPF_F_USER_STACK;
 	struct perf_callchain_entry *trace;
 	bool kernel = !user;
+	u32 max_depth;
 
 	if (unlikely(flags & ~(BPF_F_SKIP_FIELD_MASK | BPF_F_USER_STACK |
 			       BPF_F_FAST_STACK_CMP | BPF_F_REUSE_STACKID)))
 		return -EINVAL;
 
-	max_depth += skip;
-	if (max_depth > sysctl_perf_event_max_stack)
-		max_depth = sysctl_perf_event_max_stack;
+	max_depth = stack_map_calculate_max_depth(map->value_size, elem_size, flags);
 
 	trace = get_perf_callchain(regs, 0, kernel, user, max_depth,
 				   false, false);
@@ -343,7 +343,7 @@ BPF_CALL_3(bpf_get_stackid, struct pt_regs *, regs, struct bpf_map *, map,
 		/* couldn't fetch the stack trace */
 		return -EFAULT;
 
-	return __bpf_get_stackid(map, trace, flags);
+	return __bpf_get_stackid(map, trace, flags, max_depth);
 }
 
 const struct bpf_func_proto bpf_get_stackid_proto = {
@@ -375,6 +375,7 @@ BPF_CALL_3(bpf_get_stackid_pe, struct bpf_perf_event_data_kern *, ctx,
 	bool kernel, user;
 	__u64 nr_kernel;
 	int ret;
+	u32 elem_size, max_depth;
 
 	/* perf_sample_data doesn't have callchain, use bpf_get_stackid */
 	if (!(event->attr.sample_type & PERF_SAMPLE_CALLCHAIN))
@@ -393,12 +394,13 @@ BPF_CALL_3(bpf_get_stackid_pe, struct bpf_perf_event_data_kern *, ctx,
 		return -EFAULT;
 
 	nr_kernel = count_kernel_ip(trace);
-
+	elem_size = stack_map_data_size(map);
 	if (kernel) {
 		__u64 nr = trace->nr;
 
 		trace->nr = nr_kernel;
-		ret = __bpf_get_stackid(map, trace, flags);
+		max_depth = stack_map_calculate_max_depth(map->value_size, elem_size, flags);
+		ret = __bpf_get_stackid(map, trace, flags, max_depth);
 
 		/* restore nr */
 		trace->nr = nr;
@@ -410,7 +412,8 @@ BPF_CALL_3(bpf_get_stackid_pe, struct bpf_perf_event_data_kern *, ctx,
 			return -EFAULT;
 
 		flags = (flags & ~BPF_F_SKIP_FIELD_MASK) | skip;
-		ret = __bpf_get_stackid(map, trace, flags);
+		max_depth = stack_map_calculate_max_depth(map->value_size, elem_size, flags);
+		ret = __bpf_get_stackid(map, trace, flags, max_depth);
 	}
 	return ret;
 }
-- 
2.43.0

Re: [PATCH bpf-next v5 2/2] bpf: fix stackmap overflow check in __bpf_get_stackid()

[Alexei Starovoitov]

On Tue, Aug 26, 2025 at 2:24 PM Arnaud Lecomte <contact@arnaud-lcm.com> wrote:
>
> Syzkaller reported a KASAN slab-out-of-bounds write in __bpf_get_stackid()
> when copying stack trace data. The issue occurs when the perf trace
>  contains more stack entries than the stack map bucket can hold,
>  leading to an out-of-bounds write in the bucket's data array.
>
> Changes in v2:
>  - Fixed max_depth names across get stack id
>
> Changes in v4:
>  - Removed unnecessary empty line in __bpf_get_stackid
>
> Link to v4: https://lore.kernel.org/all/20250813205506.168069-1-contact@arnaud-lcm.com/
>
> Reported-by: syzbot+c9b724fbb41cf2538b7b@syzkaller.appspotmail.com
> Closes: https://syzkaller.appspot.com/bug?extid=c9b724fbb41cf2538b7b
> Signed-off-by: Arnaud Lecomte <contact@arnaud-lcm.com>
> Acked-by: Yonghong Song <yonghong.song@linux.dev>
> ---
>  kernel/bpf/stackmap.c | 23 +++++++++++++----------
>  1 file changed, 13 insertions(+), 10 deletions(-)
>
> diff --git a/kernel/bpf/stackmap.c b/kernel/bpf/stackmap.c
> index 796cc105eacb..ef8269ab8d6f 100644
> --- a/kernel/bpf/stackmap.c
> +++ b/kernel/bpf/stackmap.c
> @@ -247,7 +247,7 @@ get_callchain_entry_for_task(struct task_struct *task, u32 max_depth)
>  }
>
>  static long __bpf_get_stackid(struct bpf_map *map,
> -                             struct perf_callchain_entry *trace, u64 flags)
> +                             struct perf_callchain_entry *trace, u64 flags, u32 max_depth)
>  {
>         struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map);
>         struct stack_map_bucket *bucket, *new_bucket, *old_bucket;
> @@ -263,6 +263,8 @@ static long __bpf_get_stackid(struct bpf_map *map,
>
>         trace_nr = trace->nr - skip;
>         trace_len = trace_nr * sizeof(u64);
> +       trace_nr = min(trace_nr, max_depth - skip);
> +

The patch might have fixed this particular syzbot repro
with OOB in stackmap-with-buildid case,
but above two line looks wrong.
trace_len is computed before being capped by max_depth.
So non-buildid case below is using
memcpy(new_bucket->data, ips, trace_len);

so OOB is still there?

Re: [PATCH bpf-next v5 2/2] bpf: fix stackmap overflow check in __bpf_get_stackid()

[Song Liu]

On Fri, Aug 29, 2025 at 10:29 AM Alexei Starovoitov
<alexei.starovoitov@gmail.com> wrote:
[...]
> >
> >  static long __bpf_get_stackid(struct bpf_map *map,
> > -                             struct perf_callchain_entry *trace, u64 flags)
> > +                             struct perf_callchain_entry *trace, u64 flags, u32 max_depth)
> >  {
> >         struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map);
> >         struct stack_map_bucket *bucket, *new_bucket, *old_bucket;
> > @@ -263,6 +263,8 @@ static long __bpf_get_stackid(struct bpf_map *map,
> >
> >         trace_nr = trace->nr - skip;
> >         trace_len = trace_nr * sizeof(u64);
> > +       trace_nr = min(trace_nr, max_depth - skip);
> > +
>
> The patch might have fixed this particular syzbot repro
> with OOB in stackmap-with-buildid case,
> but above two line looks wrong.
> trace_len is computed before being capped by max_depth.
> So non-buildid case below is using
> memcpy(new_bucket->data, ips, trace_len);
>
> so OOB is still there?

+1 for this observation.

We are calling __bpf_get_stackid() from two functions: bpf_get_stackid
and bpf_get_stackid_pe. The check against max_depth is only needed
from bpf_get_stackid_pe, so it is better to just check here.

I have got the following on top of patch 1/2. This makes more sense to
me.

PS: The following also includes some clean up in __bpf_get_stack.
I include those because it also uses stack_map_calculate_max_depth.

Does this look better?

Thanks,
Song


diff --git c/kernel/bpf/stackmap.c w/kernel/bpf/stackmap.c
index 796cc105eacb..08554fb146e1 100644
--- c/kernel/bpf/stackmap.c
+++ w/kernel/bpf/stackmap.c
@@ -262,7 +262,7 @@ static long __bpf_get_stackid(struct bpf_map *map,
                return -EFAULT;

        trace_nr = trace->nr - skip;
-       trace_len = trace_nr * sizeof(u64);
+
        ips = trace->ip + skip;
        hash = jhash2((u32 *)ips, trace_len / sizeof(u32), 0);
        id = hash & (smap->n_buckets - 1);
@@ -297,6 +297,7 @@ static long __bpf_get_stackid(struct bpf_map *map,
                        return -EEXIST;
                }
        } else {
+               trace_len = trace_nr * sizeof(u64);
                if (hash_matches && bucket->nr == trace_nr &&
                    memcmp(bucket->data, ips, trace_len) == 0)
                        return id;
@@ -322,19 +323,17 @@ static long __bpf_get_stackid(struct bpf_map *map,
 BPF_CALL_3(bpf_get_stackid, struct pt_regs *, regs, struct bpf_map *, map,
           u64, flags)
 {
-       u32 max_depth = map->value_size / stack_map_data_size(map);
-       u32 skip = flags & BPF_F_SKIP_FIELD_MASK;
+       u32 elem_size = stack_map_data_size(map);
        bool user = flags & BPF_F_USER_STACK;
        struct perf_callchain_entry *trace;
        bool kernel = !user;
+       u32 max_depth;

        if (unlikely(flags & ~(BPF_F_SKIP_FIELD_MASK | BPF_F_USER_STACK |
                               BPF_F_FAST_STACK_CMP | BPF_F_REUSE_STACKID)))
                return -EINVAL;

-       max_depth += skip;
-       if (max_depth > sysctl_perf_event_max_stack)
-               max_depth = sysctl_perf_event_max_stack;
+       max_depth = stack_map_calculate_max_depth(map->value_size,
elem_size, flags);

        trace = get_perf_callchain(regs, 0, kernel, user, max_depth,
                                   false, false);
@@ -375,6 +374,7 @@ BPF_CALL_3(bpf_get_stackid_pe, struct
bpf_perf_event_data_kern *, ctx,
        bool kernel, user;
        __u64 nr_kernel;
        int ret;
+       u32 elem_size, max_depth;

        /* perf_sample_data doesn't have callchain, use bpf_get_stackid */
        if (!(event->attr.sample_type & PERF_SAMPLE_CALLCHAIN))
@@ -393,11 +393,12 @@ BPF_CALL_3(bpf_get_stackid_pe, struct
bpf_perf_event_data_kern *, ctx,
                return -EFAULT;

        nr_kernel = count_kernel_ip(trace);
-
+       elem_size = stack_map_data_size(map);
        if (kernel) {
                __u64 nr = trace->nr;

-               trace->nr = nr_kernel;
+               max_depth =
stack_map_calculate_max_depth(map->value_size, elem_size, flags);
+               trace->nr = min_t(u32, nr_kernel, max_depth);
                ret = __bpf_get_stackid(map, trace, flags);

                /* restore nr */
@@ -410,6 +411,8 @@ BPF_CALL_3(bpf_get_stackid_pe, struct
bpf_perf_event_data_kern *, ctx,
                        return -EFAULT;

                flags = (flags & ~BPF_F_SKIP_FIELD_MASK) | skip;
+               max_depth =
stack_map_calculate_max_depth(map->value_size, elem_size, flags);
+               trace->nr = min_t(u32, trace->nr, max_depth);
                ret = __bpf_get_stackid(map, trace, flags);
        }
        return ret;
@@ -428,7 +431,7 @@ static long __bpf_get_stack(struct pt_regs *regs,
struct task_struct *task,
                            struct perf_callchain_entry *trace_in,
                            void *buf, u32 size, u64 flags, bool may_fault)
 {
-       u32 trace_nr, copy_len, elem_size, num_elem, max_depth;
+       u32 trace_nr, copy_len, elem_size, max_depth;
        bool user_build_id = flags & BPF_F_USER_BUILD_ID;
        bool crosstask = task && task != current;
        u32 skip = flags & BPF_F_SKIP_FIELD_MASK;
@@ -465,13 +468,15 @@ static long __bpf_get_stack(struct pt_regs
*regs, struct task_struct *task,
        if (may_fault)
                rcu_read_lock(); /* need RCU for perf's callchain below */

-       if (trace_in)
+       if (trace_in) {
                trace = trace_in;
-       else if (kernel && task)
+               trace->nr = min_t(u32, trace->nr, max_depth);
+       } else if (kernel && task) {
                trace = get_callchain_entry_for_task(task, max_depth);
-       else
+       } else {
                trace = get_perf_callchain(regs, 0, kernel, user, max_depth,
                                           crosstask, false);
+       }

        if (unlikely(!trace) || trace->nr < skip) {
                if (may_fault)
@@ -479,9 +484,7 @@ static long __bpf_get_stack(struct pt_regs *regs,
struct task_struct *task,
                goto err_fault;
        }

-       num_elem = size / elem_size;
        trace_nr = trace->nr - skip;
-       trace_nr = (trace_nr <= num_elem) ? trace_nr : num_elem;
        copy_len = trace_nr * elem_size;

        ips = trace->ip + skip;

Re: [PATCH bpf-next v5 2/2] bpf: fix stackmap overflow check in __bpf_get_stackid()

[Alexei Starovoitov]

On Fri, Aug 29, 2025 at 11:50 AM Song Liu <song@kernel.org> wrote:
>
> On Fri, Aug 29, 2025 at 10:29 AM Alexei Starovoitov
> <alexei.starovoitov@gmail.com> wrote:
> [...]
> > >
> > >  static long __bpf_get_stackid(struct bpf_map *map,
> > > -                             struct perf_callchain_entry *trace, u64 flags)
> > > +                             struct perf_callchain_entry *trace, u64 flags, u32 max_depth)
> > >  {
> > >         struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map);
> > >         struct stack_map_bucket *bucket, *new_bucket, *old_bucket;
> > > @@ -263,6 +263,8 @@ static long __bpf_get_stackid(struct bpf_map *map,
> > >
> > >         trace_nr = trace->nr - skip;
> > >         trace_len = trace_nr * sizeof(u64);
> > > +       trace_nr = min(trace_nr, max_depth - skip);
> > > +
> >
> > The patch might have fixed this particular syzbot repro
> > with OOB in stackmap-with-buildid case,
> > but above two line looks wrong.
> > trace_len is computed before being capped by max_depth.
> > So non-buildid case below is using
> > memcpy(new_bucket->data, ips, trace_len);
> >
> > so OOB is still there?
>
> +1 for this observation.
>
> We are calling __bpf_get_stackid() from two functions: bpf_get_stackid
> and bpf_get_stackid_pe. The check against max_depth is only needed
> from bpf_get_stackid_pe, so it is better to just check here.

Good point.

> I have got the following on top of patch 1/2. This makes more sense to
> me.
>
> PS: The following also includes some clean up in __bpf_get_stack.
> I include those because it also uses stack_map_calculate_max_depth.
>
> Does this look better?

yeah. It's certainly cleaner to avoid adding extra arg to
__bpf_get_stackid()

Re: [PATCH bpf-next v5 2/2] bpf: fix stackmap overflow check in __bpf_get_stackid()

[Lecomte, Arnaud]

On 30/08/2025 02:28, Alexei Starovoitov wrote:
> On Fri, Aug 29, 2025 at 11:50 AM Song Liu <song@kernel.org> wrote:
>> On Fri, Aug 29, 2025 at 10:29 AM Alexei Starovoitov
>> <alexei.starovoitov@gmail.com> wrote:
>> [...]
>>>>   static long __bpf_get_stackid(struct bpf_map *map,
>>>> -                             struct perf_callchain_entry *trace, u64 flags)
>>>> +                             struct perf_callchain_entry *trace, u64 flags, u32 max_depth)
>>>>   {
>>>>          struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map);
>>>>          struct stack_map_bucket *bucket, *new_bucket, *old_bucket;
>>>> @@ -263,6 +263,8 @@ static long __bpf_get_stackid(struct bpf_map *map,
>>>>
>>>>          trace_nr = trace->nr - skip;
>>>>          trace_len = trace_nr * sizeof(u64);
>>>> +       trace_nr = min(trace_nr, max_depth - skip);
>>>> +
>>> The patch might have fixed this particular syzbot repro
>>> with OOB in stackmap-with-buildid case,
>>> but above two line looks wrong.
>>> trace_len is computed before being capped by max_depth.
>>> So non-buildid case below is using
>>> memcpy(new_bucket->data, ips, trace_len);
>>>
>>> so OOB is still there?
>> +1 for this observation.
>>
>> We are calling __bpf_get_stackid() from two functions: bpf_get_stackid
>> and bpf_get_stackid_pe. The check against max_depth is only needed
>> from bpf_get_stackid_pe, so it is better to just check here.
> Good point.
Nice catch, thanks !
>
>> I have got the following on top of patch 1/2. This makes more sense to
>> me.
>>
>> PS: The following also includes some clean up in __bpf_get_stack.
>> I include those because it also uses stack_map_calculate_max_depth.
>>
>> Does this look better?
> yeah. It's certainly cleaner to avoid adding extra arg to
> __bpf_get_stackid()
>
Are Song patches going to be applied then ?  Or should I raise a new 
revision
  of the patch with Song's modifications with a Co-developped tag ?
Thanks for your guidance in advance,
Arnaud

Re: [PATCH bpf-next v5 2/2] bpf: fix stackmap overflow check in __bpf_get_stackid()

[Alexei Starovoitov]

On Sat, Aug 30, 2025 at 10:13 AM Lecomte, Arnaud <contact@arnaud-lcm.com> wrote:
>
>
> On 30/08/2025 02:28, Alexei Starovoitov wrote:
> > On Fri, Aug 29, 2025 at 11:50 AM Song Liu <song@kernel.org> wrote:
> >> On Fri, Aug 29, 2025 at 10:29 AM Alexei Starovoitov
> >> <alexei.starovoitov@gmail.com> wrote:
> >> [...]
> >>>>   static long __bpf_get_stackid(struct bpf_map *map,
> >>>> -                             struct perf_callchain_entry *trace, u64 flags)
> >>>> +                             struct perf_callchain_entry *trace, u64 flags, u32 max_depth)
> >>>>   {
> >>>>          struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map);
> >>>>          struct stack_map_bucket *bucket, *new_bucket, *old_bucket;
> >>>> @@ -263,6 +263,8 @@ static long __bpf_get_stackid(struct bpf_map *map,
> >>>>
> >>>>          trace_nr = trace->nr - skip;
> >>>>          trace_len = trace_nr * sizeof(u64);
> >>>> +       trace_nr = min(trace_nr, max_depth - skip);
> >>>> +
> >>> The patch might have fixed this particular syzbot repro
> >>> with OOB in stackmap-with-buildid case,
> >>> but above two line looks wrong.
> >>> trace_len is computed before being capped by max_depth.
> >>> So non-buildid case below is using
> >>> memcpy(new_bucket->data, ips, trace_len);
> >>>
> >>> so OOB is still there?
> >> +1 for this observation.
> >>
> >> We are calling __bpf_get_stackid() from two functions: bpf_get_stackid
> >> and bpf_get_stackid_pe. The check against max_depth is only needed
> >> from bpf_get_stackid_pe, so it is better to just check here.
> > Good point.
> Nice catch, thanks !
> >
> >> I have got the following on top of patch 1/2. This makes more sense to
> >> me.
> >>
> >> PS: The following also includes some clean up in __bpf_get_stack.
> >> I include those because it also uses stack_map_calculate_max_depth.
> >>
> >> Does this look better?
> > yeah. It's certainly cleaner to avoid adding extra arg to
> > __bpf_get_stackid()
> >
> Are Song patches going to be applied then ?  Or should I raise a new
> revision
>   of the patch with Song's modifications with a Co-developped tag ?

Pls resubmit and retest with a tag.